Methods for purifying cells derived from pluripotent stem cells

ABSTRACT

The present invention is directed to methods to differentiate pluripotent stem cells. In particular, the present invention provides methods of characterization of cells differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage utilizing unique surface markers. The present invention also provides methods to enrich or sort cells expressing markers characteristic of the pancreatic endocrine lineage. The present invention also provides methods to deplete cells that may contaminate populations of cells expressing markers characteristic of the pancreatic endocrine lineage formed by the methods of the present invention, thereby reducing the incidence of tumor formation in vivo following transplantation.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patent application Ser. No. 13/036,476, filed Feb. 28, 2011 (now allowed), which claims the benefit to U.S. Provisional Patent Application No. 61/309,193, filed Mar. 1, 2010, the contents of all of which are incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention is directed to methods to differentiate pluripotent stem cells. In particular, the present invention provides methods of characterization of cells differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage utilizing unique surface markers. The present invention also provides methods to enrich or sort cells expressing markers characteristic of the pancreatic endocrine lineage. The present invention also provides methods to deplete cells that may contaminate populations of cells expressing markers characteristic of the pancreatic endocrine lineage formed by the methods of the present invention, thereby reducing the incidence of tumor formation in vivo following transplantation.

BACKGROUND

Pluripotent stem cells have the potential to produce differentiated cell types comprising all somatic tissues and organs. Treatment of diabetes using cell therapy is facilitated by the production of large numbers of cells that are able to function similarly to human islets. Accordingly, there is need for producing these cells derived from pluripotent stem cells, as well as reliable methods for purifying such cells.

Proteins and other cell surface markers found on pluripotent stem cell and cell populations derived from pluripotent stem cells are useful in preparing reagents for the separation and isolation of these populations. Cell surface markers are also useful in the further characterization of these cells.

In one example, WO2009131568 discloses a method of purifying a gut endoderm cell comprising: a) exposing a population of cells derived from pluripotent stem cells comprising a gut endoderm cell to a ligand which binds to a cell surface marker expressed on the gut endoderm cell, wherein said cell surface marker is selected from the group consisting of CD49e, CD99, CD165, and CD334; and b) separating the gut endoderm cell from cells derived from pluripotent stem cells which do not bind to the ligand, thereby purifying said gut endoderm cell.

In another example, WO2010000415 discloses the use of an antibody that binds to the antigen TNAP, or functional fragments of the antibody, alone or in combination with an antibody that binds to CD56, or functional fragments of the antibody, for the isolation of stem cells having adipocytic, chondrocytic and pancreatic differentiation potential.

In another example, U.S. Pat. No. 7,371,576 discloses the discovery of a selective cell surface marker that permits the selection of a unique subset of pancreatic stems cells having a high propensity to differentiate into insulin producing cells or into insulin producing cell aggregates.

In another example, U.S. Pat. No. 7,585,672 discloses a method to enrich a culture derived from human embryonic stem cells for cells of endoderm and pancreatic lineages, the method comprising the steps of (a) culturing intact colonies of human embryonic stem cells to form whole, intact embryoid bodies surrounded by visceral yolk sac (VYS) cells, wherein the human embryonic stem cells express Oct-4, surface stage-specific embryonic antigen-3/4 (SSEA 3/4) and epithelial cell adhesion molecule (EpCAM); (b) culturing the embryoid bodies of step (a) under conditions that permit the embryoid body cells to differentiate into a cell population containing cells of the endoderm and pancreatic lineages; (c) dispersing the cell population of step (b) into single cells; (d) selecting against the expression of SSEA 3/4 positive cells to remove undifferentiated cells from the cells of step (c); (e) selecting against the expression of SSEA-1 positive cells to remove VYS cells from the remaining cells of step (d); and (f) selecting from among the remaining cells of step (e) for the expression of EpCAM positive cells to enrich for cells of endoderm and pancreatic lineages.

U.S. Pat. No. 7,585,672 also discloses a method to enrich a culture derived from human embryonic stem cells for cells of endoderm and pancreatic lineages, the method comprising the steps of (a) culturing intact colonies of human embryonic stem cells to form whole, intact embryoid bodies surrounded by visceral yolk sac (VYS) cells, wherein the human embryonic stem cells express Oct-4, surface stage-specific embryonic antigen-3/4 (SSEA 3/4) and epithelial cell adhesion molecule (EpCAM); (b) culturing the embryoid bodies of step (a) under conditions that permit the embryoid body cells to differentiate into a cell population containing cells of the endoderm and pancreatic lineages; (c) treating the cell population of step (b) with an effective amount of fibroblast growth factor 10 (FGFI 0); and (d) dispersing the cell population of step (c) into single cells enriched for cells of endoderm and pancreatic lineages (e) selecting against the expression of SSEA-3/4 positive cells to remove undifferentiated stem cells from the cells of step (d); (f) selecting against the expression of SSEA-1 positive cells to remove VYS cells from the cells of step (e); and (g) selecting from among the remaining cells of step (f) for the expression of EpCAM positive cells to enrich for cells of endoderm and pancreatic lineages.

U.S. Pat. No. 7,585,672 also discloses an enrichment method for the creation of a stem cell derived cell population which does not have tumorigenic capability comprising the steps of (a) culturing intact colonies of human embryonic stem cells to form whole, intact embryoid bodies surrounded by visceral yolk sac (VYS) cells, wherein the human embryonic stem cells express Oct-4, surface stage-specific embryonic antigen-3/4 (SSEA 3/4) and epithelial cell adhesion molecule (EpCAM); (b) culturing the embryoid bodies of step (a) under conditions that permit the embryoid body cells to differentiate into a cell population containing cells of the endoderm and pancreatic lineages; (c) dispersing the cell population of step (b) into single cells; (d) selecting against the expression of SSEA 3/4 positive cells to remove undifferentiated cells from the cells of step (c); (e) selecting against the expression of SSEA-1 positive cells to remove VYS cells from the cells of step (d); and (f) selecting from among the remaining cells of step (e) for the expression of EpCAM positive cells, the resulting cells not forming teratomas when injected in immunocompromised mice.

In another example, US20050260749 discloses a method to enrich a culture derived from stem cells for cells of endoderm and pancreatic lineages, the method comprising the steps of culturing stem cells into the formation of embryoid bodies; and selecting among embryoid bodies for the expression of the species appropriate cell surface stage-specific embryonic and culturing only the embryoid bodies which do not express cell surface stage-specific antigen for differentiation into endoderm and pancreatic cells.

In another example, US20100003749 discloses an isolated pancreatic stem cell population, wherein the pancreatic stem cell population is enriched for CD133+CD49f+ pancreatic stem cells.

US20100003749 further discloses the isolation of pancreatic stem cells from primary pancreatic tissue occurs by selecting from a population of pancreatic cells, pancreatic-derived cells, or gastrointestinal-derived cells for cells that are CD133+, CD49f+, or CD133+CD49f+; removing the cells that are CD15+, wherein the remaining cells are CD15−; introducing the remaining cells to a serum-free culture medium containing one or more growth factors; and proliferating the remaining cells in the culture medium.

In another example, Dorrell et al. state: “We have developed a novel panel of cell-surface markers for the isolation and study of all major cell types of the human pancreas. Hybridomas were selected after subtractive immunization of Balb/C mice with intact or dissociated human islets and assessed for cell-type specificity and cell-surface reactivity by immunohistochemistry and flow cytometry. Antibodies were identified by specific binding of surface antigens on islet (panendocrine or α-specific) and nonislet pancreatic cell subsets (exocrine and duct). These antibodies were used individually or in combination to isolate populations of α, β, exocrine, or duct cells from primary human pancreas by FACS and to characterize the detailed cell composition of human islet preparations. They were also employed to show that human islet expansion cultures originated from nonendocrine cells and that insulin expression levels could be increased to up to 1% of normal islet cells by subpopulation sorting and overexpression of the transcription factors Pdx-1 and ngn3, an improvement over previous results with this culture system. These methods permit the analysis and isolation of functionally distinct pancreatic cell populations with potential for cell therapy.” (Stem Cell Research, Volume 1, Issue 3, September 2008, Pages 155-156).

In another example, Sugiyama et al. state: “We eventually identified two antigens, called CD133 and CD49f, useful for purifying NGN3+ cells from mice. CD133 (also called prominin-1) is a transmembrane protein of unknown function and a known marker of haematopoietic progenitor and neural stem cells. CD49f is also called a6-integrin, and a receptor subunit for laminin. By combining antibodies that recognize CD133 and CD49f, we fractionated four distinct pancreatic cell populations. Immunostaining and RT-PCR revealed that the CD49fhigh CD133+ cell population (‘fraction I’, 50% of input) comprised mainly differentiated exocrine cells that express CarbA. The CD49flow CD133− fraction (‘fraction III’, 10% of input) included hormone+ cells expressing endocrine products like insulin and glucagon. By contrast, the CD49flow CD133+ fraction (called ‘fraction II’, 13% of input) contained NGN3+ cells, but not hormone+ cells. Approximately 8% of fraction II cells produced immunostainable NGN3. In the CD49f−CD133− fraction (‘fraction IV’, 25% of input), we did not detect cells expressing NGN3, CarbA or islet hormones.” (Diabetes, Obesity and Metabolism, Volume 10, Issue s4, Pages 179-185).

In another example, Fujikawa et al. state: “When CD45− TER119− side-scatterlow GFPhigh cells were sorted, α-fetoprotein-positive immature endoderm-characterized cells, having high growth potential, were present in this population. Clonal analysis and electron microscopic evaluation revealed that each single cell of this population could differentiate not only into hepatocytes, but also into biliary epithelial cells, showing their bilineage differentiation activity. When surface markers were analyzed, they were positive for Integrin-α6 and -β1, but negative for c-Kit and Thy1.1.” (Journal of Hepatlogy, Vol 39, pages 162-170).

In another example, Zhao et al. state: “In this study, we first identified N-cadherin as a surface marker of hepatic endoderm cells for purification from hES cell-derivates, and generated hepatic progenitor cells from purified hepatic endoderm cells by co-culture with murine embryonic stromal feeders (STO) cells. These hepatic progenitor cells could expand and be passaged for more than 100 days. Interestingly, they co-expressed the early hepatic marker AFP and biliary lineage marker KRT7, suggesting that they are a common ancestor of both hepatocytes and cholangiocytes. Moreover, these progenitor cells could be expanded extensively while still maintaining the bipotential of differentiation into hepatocyte-like cells and cholangiocyte-like cells, as verified by both gene expression and functional assays. Therefore, this work offers a new in vitro model for studying liver development, as well as a new source for cell therapy based on hepatic progenitors.” (PLoS ONE 4(7): e6468. doi:10.1371/journal.pone.0006468).

In another example, Cai et al. state: “To further increase the PDX1+ cell purity, we sorted the activin A-induced cells using CXCR4 . . . , a marker for ES cell-derived endodermal cells. Sorting with CXCR4 enriched the endodermal cell population because nearly all the cells in the CXCR4+ population were positive for the endodermal cell marker SOX17, and >90% of the cells were positive for FOXA2.” (Journal of Molecular Cell Biology Advance Access originally published online on Nov. 12, 2009. Journal of Molecular Cell Biology 2010 2(1):50-60; doi:10.1093/jmcb/mjp037).

In another example, Koblas et al. state: “We found that population of human CD133-positive pancreatic cells contains endocrine progenitors expressing neurogenin-3 and cells expressing human telomerase, ABCG2, Oct-3/4, Nanog, and Rex-1, markers of pluripotent stem cells. These cells were able to differentiate into insulin-producing cells in vitro and secreted C-peptide in a glucose-dependent manner. Based on our results, we suppose that the CD133 molecule represents another cell surface marker suitable for identification and isolation of pancreatic endocrine progenitors”. (Transplant Proc. 2008 March; 40(2):415-8).

In another example, Sugiyama et al. state: “we found CD133 was expressed by NGN3+ cells. CD133 appeared to be localized to the apical membrane of pancreatic ductal epithelial cells.” (PNAS 2007 104:175-180; published online before print Dec. 26, 2006, doi:10.1073/pnas.0609490104).

In another example, Kobayashi et al. state: “The embryonic pancreatic epithelium, and later the ductal epithelium, is known to give rise to the endocrine and exocrine cells of the developing pancreas, but no specific surface marker for these cells has been identified. Here, we utilized Dolichos Biflorus Agglutinin (DBA) as a specific marker of these epithelial cells in developing mouse pancreas. From the results of an immunofluorescence study using fluorescein-DBA and pancreatic specific cell markers, we found that DBA detects specifically epithelial, but neither differentiating endocrine cells nor acinar cells. We further applied this marker in an immunomagnetic separation system (Dynabead system) to purify these putative multi-potential cells from a mixed developing pancreatic cell population. This procedure could be applied to study differentiation and cell lineage selections in the developing pancreas, and also may be applicable to selecting pancreatic precursor cells for potential cellular engineering.” (Biochemical and Biophysical Research Communications, Volume 293, Issue 2, 3 May 2002, Pages 691-697).

Identification of markers expressed by cells derived from pluripotent stem cells would expand the understanding of these cells, aid in their identification in vivo and in vitro, and would enable their positive enrichment in vitro for study and use. Thus, there remains a need for tools that are useful in isolating and characterizing cells derived from pluripotent stem cells, in particular, cells expressing markers characteristic of the pancreatic endocrine lineage.

SUMMARY

In one embodiment, the present invention provides a method to differentiate a population of pluripotent stem cells into a population of cells expressing markers characteristic of the pancreatic endocrine lineage, comprising the steps of:

-   -   a. Culturing a population of pluripotent stem cells,     -   b. Differentiating the population of pluripotent stem cells into         a population of cells expressing markers characteristic of the         definitive endoderm lineage,     -   c. Differentiating the population of cells expressing markers         characteristic of the definitive endoderm lineage into cells         expressing markers characteristic of the primitive gut tube         lineage,     -   d. Differentiating the population of cells expressing markers         characteristic of the primitive gut tube lineage into a         population of cells expressing markers characteristic of the         pancreatic endoderm lineage, and     -   e. Differentiating the population of cells expressing markers         characteristic of the pancreatic endoderm lineage into a         population cells expressing markers characteristic of the         pancreatic endocrine lineage.

In one embodiment, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is transplanted into an animal, wherein the cells expressing markers characteristic of the pancreatic endocrine lineage form insulin producing cells. In one embodiment, the efficiency of the formation of insulin producing cells is enhanced by enriching the population for cells expressing markers characteristic of the pancreatic endocrine lineage prior to transplantation.

In one embodiment, the efficiency of the formation of insulin producing cells is determined by measuring the time taken for the expression of C-peptide to reach detectable levels following transplantation.

In an alternate embodiment, the enrichment decreases the ability of the transplanted cells to form teratomas following transplantation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), NKX2.2 (panel e), and PAX4 (panel f) in populations of CD56⁺CD13⁻, CD56⁻CD13⁻ and CD56⁻CD13⁺ cells, as detected via real-time PCR. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 2 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), NKX2.2 (panel e), and PAX4 (panel f), as detected via real-time PCR, in populations of cells sorted using an antibody to CD133. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 3 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), and NKX6.1 (panel d), as detected via real-time PCR, in populations of cells sorted using an antibody to CD49c. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 4 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), insulin (panel e), and glucagon (panel f), as detected via real-time PCR, in populations of cells sorted using antibodies to CD56 and CD15. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 5 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), NKX2.2 (panel e), PAX-4 (panel f), glucagon (panel g) and insulin (panel h) as detected via real-time PCR, in populations of cells sorted using an antibody to CD15. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 6 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), NKX2.2 (panel e), insulin (panel f), and glucagon (panel g) as detected via real-time PCR, in populations of cells sorted using antibodies to CD56 and CD57. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 7 shows the expression of ZIC1 (panel a), albumin (panel b), CDX2 (panel c), NGN3 (panel d), PAX4 (panel e), NEUROD (panel f), NKX6.1 (panel g), PTF1 alpha (panel h), and PDX1 (panel i), as detected via real-time PCR, in populations of cells sorted using antibodies to CD56 and CD184. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 8 shows the expression of NEUROD (panel a), NGN3 (panel b), insulin (panel c), and glucagon (panel d), as detected via real-time PCR, in populations of cells sorted using an antibody to CD98. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 9 shows the expression of NEUROD (panel a), NGN3 (panel b), PDX1 (panel c), NKX6.1 (panel d), NKX2.2 (panel e), and PAX4 (panel f), as detected via real-time PCR, in populations of cells sorted using an antibody to CD47. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 10 shows the expression of PDX-1 (panel a), NKX6.1 (panel b), NKX2.2 (panel c), PAX-4 (panel d), PTF1a (panel e), NGN3 (panel f), Insulin (panel g) and glucagon (panel h) as detected via real-time PCR, in populations of cells sorted using an antibody to CD47. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 11 shows the expression of HNF4 alpha (panel a), and LIF receptor (panel b), as detected via real-time PCR, in populations of cells sorted using an antibody to the LIF receptor. Fold expression is shown relative to unsorted cells at DAY 2 of Stage II of the differentiation protocol outlined in Example 1.

FIG. 12 shows the expression of OCT4 (panel a), NANOG (panel b), SOX2 (panel c), and goosecoid (panel d), as detected via real-time PCR, in populations of cells depleted of cells expressing SSEA4 using magnetic beads. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

FIG. 13 shows the expression of OCT4 (panel a), NANOG (panel b), SOX2 (panel c), and goosecoid (panel d), as detected via real-time PCR, in populations of cells depleted of cells expressing SSEA4 using FACS. Fold expression is shown relative to undifferentiated H1 embryonic stem cells.

DETAILED DESCRIPTION

For clarity of disclosure, and not by way of limitation, the detailed description of the invention is divided into the following subsections that describe or illustrate certain features, embodiments or applications of the present invention.

Definitions

“β-cell lineage” refers to cells with positive gene expression for the transcription factor PDX-1 and at least one of the following transcription factors: NGN3, NKX2.2, NKX6.1, NEUROD, ISL1, HNF-3 beta, MAFA, PAX4, and PAX6. Cells expressing markers characteristic of the β cell lineage include β cells.

“Cells expressing markers characteristic of the definitive endoderm lineage” as used herein refers to cells expressing at least one of the following markers: SOX17, GATA4, HNF-3 beta, GSC, CER1, Nodal, FGF8, Brachyury, Mix-like homeobox protein, FGF4, CD48, eomesodermin (EOMES), DKK4, FGF17, GATA6, CD184, C-Kit, CD99, or OTX2. Cells expressing markers characteristic of the definitive endoderm lineage include primitive streak precursor cells, primitive streak cells, mesendoderm cells and definitive endoderm cells.

“Cells expressing markers characteristic of the primitive gut tube lineage” refers to cells expressing at least one of the following markers: HNF-1 beta, or HNF-4 alpha.

“Cells expressing markers characteristic of the pancreatic endoderm lineage” as used herein refers to cells expressing at least one of the following markers: PDX1, HNF-1 beta, PTF-1 alpha, HNF6, or HB9. Cells expressing markers characteristic of the pancreatic endoderm lineage include pancreatic endoderm cells.

“Cells expressing markers characteristic of the pancreatic endocrine lineage” as used herein refers to cells expressing at least one of the following markers: NGN3, NEUROD, ISL1, PDX1, NKX6.1, PAX4, or PTF-1 alpha. Cells expressing markers characteristic of the pancreatic endocrine lineage include pancreatic endocrine cells, pancreatic hormone expressing cells, and pancreatic hormone secreting cells, and cells of the β-cell lineage.

“Definitive endoderm” as used herein refers to cells which bear the characteristics of cells arising from the epiblast during gastrulation and which form the gastrointestinal tract and its derivatives. Definitive endoderm cells express the following markers: CD184, HNF-3 beta, GATA4, SOX17, Cerberus, OTX2, goosecoid, c-Kit, CD99, and Mix11.

“Markers” as used herein, are nucleic acid or polypeptide molecules that are differentially expressed in a cell of interest. In this context, differential expression means an increased level for a positive marker and a decreased level for a negative marker. The detectable level of the marker nucleic acid or polypeptide is sufficiently higher or lower in the cells of interest compared to other cells, such that the cell of interest can be identified and distinguished from other cells using any of a variety of methods known in the art.

“Pancreatic endocrine cell” or “pancreatic hormone expressing cell” as used herein refers to a cell capable of expressing at least one of the following hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide.

“Pancreatic hormone secreting cell” as used herein refers to a cell capable of secreting at least one of the following hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide.

“Pre-primitive streak cell” as used herein refers to a cell expressing at least one of the following markers: Nodal, or FGF8.

“Primitive streak cell” as used herein refers to a cell expressing at least one of the following markers: Brachyury, Mix-like homeobox protein, or FGF4.

Stem cells are undifferentiated cells defined by their ability at the single cell level to both self-renew and differentiate to produce progeny cells, including self-renewing progenitors, non-renewing progenitors, and terminally differentiated cells. Stem cells are also characterized by their ability to differentiate in vitro into functional cells of various cell lineages from multiple germ layers (endoderm, mesoderm and ectoderm), as well as to give rise to tissues of multiple germ layers following transplantation and to contribute substantially to most, if not all, tissues following injection into blastocysts.

Stem cells are classified by their developmental potential as: (i) totipotent, meaning able to give rise to all embryonic and extraembryonic cell types; (ii) pluripotent, meaning able to give rise to all embryonic cell types; (iii) multipotent, meaning able to give rise to a subset of cell lineages, but all within a particular tissue, organ, or physiological system (for example, hematopoietic stem cells (HSC) can produce progeny that include HSC (self-renewal), blood cell restricted oligopotent progenitors and all cell types and elements (e.g., platelets) that are normal components of the blood); (iv) oligopotent, meaning able to give rise to a more restricted subset of cell lineages than multipotent stem cells; and (v) unipotent, meaning able to give rise to a single cell lineage (e.g., spermatogenic stem cells).

Differentiation is the process by which an unspecialized (“uncommitted”) or less specialized cell acquires the features of a specialized cell such as, for example, a nerve cell or a muscle cell. A differentiated or differentiation-induced cell is one that has taken on a more specialized (“committed”) position within the lineage of a cell. The term “committed”, when applied to the process of differentiation, refers to a cell that has proceeded in the differentiation pathway to a point where, under normal circumstances, it will continue to differentiate into a specific cell type or subset of cell types, and cannot, under normal circumstances, differentiate into a different cell type or revert to a less differentiated cell type. Dedifferentiation refers to the process by which a cell reverts to a less specialized (or committed) position within the lineage of a cell. As used herein, the lineage of a cell defines the heredity of the cell, that is, which cells it came from and what cells it can give rise to. The lineage of a cell places the cell within a hereditary scheme of development and differentiation. A lineage-specific marker refers to a characteristic specifically associated with the phenotype of cells of a lineage of interest and can be used to assess the differentiation of an uncommitted cell to the lineage of interest.

Various terms are used to describe cells in culture. “Maintenance” refers generally to cells placed in a growth medium under conditions that facilitate cell growth and/or division that may or may not result in a larger population of the cells. “Passaging” refers to the process of removing the cells from one culture vessel and placing them in a second culture vessel under conditions that facilitate cell growth and/or division.

A specific population of cells, or a cell line, is sometimes referred to or characterized by the number of times it has been passaged. For example, a cultured cell population that has been passaged ten times may be referred to as a P10 culture. The primary culture, that is, the first culture following the isolation of cells from tissue, is designated P0. Following the first subculture, the cells are described as a secondary culture (P1 or passage 1). After the second subculture, the cells become a tertiary culture (P2 or passage 2), and so on. It will be understood by those of skill in the art that there may be many population doublings during the period of passaging; therefore the number of population doublings of a culture is greater than the passage number. The expansion of cells (that is, the number of population doublings) during the period between passaging depends on many factors, including but not limited to the seeding density, substrate, medium, growth conditions, and time between passaging.

Enrichment of Cells Expressing Markers Characteristic of the Pancreatic Endocrine Lineage

In one embodiment, the present invention provides a method to differentiate a population of pluripotent stem cells into a population of cells expressing markers characteristic of the pancreatic endocrine lineage, comprising the steps of:

-   -   a. Culturing a population of pluripotent stem cells,     -   b. Differentiating the population of pluripotent stem cells into         a population of cells expressing markers characteristic of the         definitive endoderm lineage,     -   c. Differentiating the population of cells expressing markers         characteristic of the definitive endoderm lineage into cells         expressing markers characteristic of the primitive gut tube         lineage,     -   d. Differentiating the population of cells expressing markers         characteristic of the primitive gut tube lineage into a         population of cells expressing markers characteristic of the         pancreatic endoderm lineage, and     -   e. Differentiating the population of cells expressing markers         characteristic of the pancreatic endoderm lineage into a         population cells expressing markers characteristic of the         pancreatic endocrine lineage.

In one embodiment, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is transplanted into an animal, wherein the cells expressing markers characteristic of the pancreatic endocrine lineage form insulin producing cells. In one embodiment, the efficiency of the formation of insulin producing cells is enhanced by enriching the population for cells expressing markers characteristic of the pancreatic endocrine lineage prior to transplantation.

In one embodiment, the efficiency of the formation of insulin producing cells is determined by measuring the time taken for the expression of C-peptide to reach detectable levels following transplantation.

In an alternate embodiment, the enrichment decreases the ability of the transplanted cells to form teratomas following transplantation.

Cells expressing markers of the pancreatic endocrine lineage are identified or selected through the binding of antigens, found on the surfaces of the cells, to reagents that specifically bind the cell surface antigen.

In an alternate embodiment, cells expressing markers characteristic of the pancreatic endocrine lineage are further differentiated into insulin producing cells, prior to transplantation into an animal. Insulin producing cells are identified or selected through the binding of antigens, found on the surfaces of the cells, to reagents that specifically bind the cell surface antigen.

In an alternate embodiment, the present invention provides a method to differentiate a population of pluripotent stem cells into a population of cells expressing markers characteristic of the pancreatic endocrine lineage, comprising the steps of:

-   -   a. Culturing a population of pluripotent stem cells,     -   b. Differentiating the population of pluripotent stem cells into         a population of cells expressing markers characteristic of the         definitive endoderm lineage,     -   c. Differentiating the population of cells expressing markers         characteristic of the definitive endoderm lineage into cells         expressing markers characteristic of the primitive gut tube         lineage,     -   d. Enriching the population of cells that express markers         characteristic of the primitive gut tube lineage,     -   e. Differentiating the population of cells expressing markers         characteristic of the primitive gut tube lineage into a         population of cells expressing markers characteristic of the         pancreatic endoderm lineage, and     -   f. Differentiating the population of cells expressing markers         characteristic of the pancreatic endoderm lineage into a         population cells expressing markers characteristic of the         pancreatic endocrine lineage.

In one embodiment, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is transplanted into an animal, wherein the cells expressing markers characteristic of the pancreatic endocrine lineage form insulin producing cells. In one embodiment, the efficiency of the formation of insulin producing cells is enhanced by enriching the population of cells that express markers characteristic of the primitive gut tube lineage prior to transplantation.

Cells expressing markers of the primitive gut tube lineage are identified or selected through the binding of antigens, found on the surfaces of the cells, to reagents that specifically bind the cell surface antigen.

Surface Antigens that Facilitate Enrichment of Cells Expressing Markers Characteristic of the Pancreatic Endocrine Lineage

In one embodiment, prior to transplantation into an animal, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is treated with at least one reagent that is capable of binding to a marker selected from the group consisting of CD9, CD13, CD15, CD47, CD56, CD73, CD117, CD133, CD184, CD200, CD318, CD326 and SSEA4.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are positive for the expression of the marker CD56 and negative for the expression of the marker CD13.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are positive for the expression of the marker CD56 and negative for the expression of the marker CD15.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are negative for the expression of the marker CD133.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are negative for the expression of the marker CD15.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are positive for the expression of the marker CD184.

In one embodiment, treatment with the at least one reagent results in a population of cells expressing markers characteristic of the pancreatic endocrine lineage that are negative for the expression of the marker SSEA4.

Surface Antigens that Facilitate Enrichment of Insulin Producing Cells

In one embodiment, prior to transplantation into an animal, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is further differentiated into a population of insulin producing cells. The population of insulin producing cells is treated with at least one reagent that is capable of binding to a marker selected from the group consisting of CD47, CD56, CD57 CD98 and SSEA4.

In one embodiment, treatment with the at least one reagent results in a population of insulin producing cells that are positive for the expression of the marker CD56 and CD57. Alternatively, the population of insulin producing cells may be positive for the expression of CD98. Alternatively, the population of insulin producing cells may be negative for the expression of CD47.

In one embodiment, treatment with the at least one reagent results in a population of insulin producing cells that are negative for the expression of the marker SSEA4.

CD13 is expressed on the majority of peripheral blood monocytes and granulocytes. It is also expressed by the majority of acute myeloid leukemias, chronic myeloid leukemias in myeloid blast crisis, a smaller percentage of lymphoid leukemias and myeloid cell lines. CD13 is also found in several types of non hematopoietic cells such as fibroblasts and endothelial cells and in a soluble form in blood plasma. CD13 is not expressed on B cells, T cells, platelets or erythrocytes. CD13 plays a role in biologically active peptide metabolism, in the control of growth and differentiation, in phagocytosis and in bactericidal/tumoricidal activities. CD13 also serves as a receptor for human coronaviruses (HCV).

CD15 is a carbohydrate adhesion molecule that can be expressed on glycoproteins, glycolipids and proteoglycans. CD15 mediates phagocytosis and chemotaxis, found on neutrophils; expressed in patients with Hodgkin disease, some B-cell chronic lymphocytic leukemias, acute lymphoblastic leukemias, and most acute nonlymphocytic leukemias. It is also called Lewis x and SSEA-1 (stage specific embryonic antigen 1) and represents a marker for murine pluripotent stem cells, in which it plays an important role in adhesion and migration of the cells in the preimplantation embryo.

CD47 is a membrane protein, which is involved in the increase in intracellular calcium concentration that occurs upon cell adhesion to extracellular matrix. The protein is also a receptor for the C-terminal cell binding domain of thrombospondin, and it may play a role in membrane transport and signal transduction.

CD56, also known as Neural Cell Adhesion Molecule (NCAM) is a homophilic binding glycoprotein expressed on the surface of neurons, glia, skeletal muscle and natural killer cells. NCAM has been implicated as having a role in cell-cell adhesion, neurite outgrowth, synaptic plasticity, and learning and memory.

CD57 also known as HNK-1 or Leu-7, is an antigenic oligosaccharide moiety detected on extracellular proteins of certain cell types. In blood, CD57 is found on 15-20% of mononuclear cells, including subsets of NK and T cells, though not on erythrocytes, monocytes, granulocytes, or platelets. Also, CD57 expression can be found on a variety of neural cell types.

CD98 is a glycoprotein that comprises the light subunit of the Large neutral Amino acid Transporter (LAT1). LAT1 is a heterodimeric membrane transport protein that preferentially transports neutral branched (valine, leucine, isoleucine) and aromatic (tryptophan, tyrosine) amino acids.

CD133 is a glycoprotein also known in humans and rodents as Prominin 1 (PROM1). It is a member of pentaspan transmembrane glycoproteins (5-transmembrane, 5-TM), which specifically localizes to cellular protrusions. CD133 is expressed in hematopoietic stem cells, endothelial progenitor cells, glioblastomas, neuronal and glial stem cells. See Corbeil et al, Biochem Biophys Res Commun 285 (4): 939-44, 2001. doi:10.1006/bbrc.2001.5271. PMID 11467842.

Surface Antigens that Facilitate Enrichment of Cells Expressing Markers Characteristic of the Primitive Gut Tube Lineage

In an alternate embodiment, the present invention provides a method to differentiate a population of pluripotent stem cells into a population of cells expressing markers characteristic of the pancreatic endocrine lineage, comprising the steps of:

-   -   a. Culturing a population of pluripotent stem cells,     -   b. Differentiating the population of pluripotent stem cells into         a population of cells expressing markers characteristic of the         definitive endoderm lineage,     -   c. Differentiating the population of cells expressing markers         characteristic of the definitive endoderm lineage into cells         expressing markers characteristic of the primitive gut tube         lineage,     -   d. Enriching the population of cells that express markers         characteristic of the primitive gut tube lineage,     -   e. Differentiating the population of cells expressing markers         characteristic of the primitive gut tube lineage into a         population of cells expressing markers characteristic of the         pancreatic endoderm lineage, and     -   f. Differentiating the population of cells expressing markers         characteristic of the pancreatic endoderm lineage into a         population cells expressing markers characteristic of the         pancreatic endocrine lineage.

In one embodiment, the population of cells expressing markers characteristic of the pancreatic endocrine lineage is transplanted into an animal, wherein the cells expressing markers characteristic of the pancreatic endocrine lineage form insulin producing cells. In one embodiment, the efficiency of the formation of insulin producing cells is enhanced by enriching the population of cells that express markers characteristic of the primitive gut tube lineage prior to transplantation.

The population of cells that express markers characteristic of the primitive gut tube lineage is treated with at least one reagent that is capable of binding to the LIF receptor.

The cells expressing markers characteristic of the pancreatic endocrine lineage, cells expressing markers characteristic of the primitive gut tube lineage, or insulin producing cells may be enriched, depleted, isolated, separated, sorted and/or purified as further described in the examples. As used herein, the terms “enriched” or “purified” or enriched or purified due to depletion of other known cell populations, indicate that the cells has been subject to some selection process so that the population is enriched and/or purified. Also, the subject cells are also considered relatively enriched and/or purified, i.e. there is significantly more of a particular differentiated cell population as compared to another cell population, or as compared to pluripotent stem cells before “enrichment” or “purification”, or as compared to the original or initial cell culture.

Enriching or purifying for a given differentiated cell type may involve “depleting” or “separating” or “sorting” one or more known cell types from another cell type. In one embodiment, a population of cells may be purified by depleting an unwanted differentiated cell type. It may be advantageous to enrich and purify a cell expressing markers characteristic of the pancreatic endocrine lineage by depleting the culture of known or unknown cell types. In this way, the enriched or purified cell population would not have the bound or attached antibody. Because there is no need to remove the antibody from the purified population, the use of the enriched or purified cells for cell therapies may be improved.

Methods for enriching, depleting, isolating, separating, sorting and/or purifying may include, for example, selective culture conditions, wherein the culture conditions are detrimental to any undesirable cell types.

Methods for enriching, depleting, isolating, separating, sorting and/or purifying may also include, for example, antibody-coated magnetic beads, affinity chromatography and “panning” with antibody attached to a solid matrix or solid phase capture medium, e.g. plate, column or other convenient and available technique. Techniques providing accurate separation include flow cytometry methods which are useful for measuring cell surface and intracellular parameters, as well as shape change and granularity and for analyses of beads used as antibody- or probe-linked reagents. Readouts from flow cytometry assays include, but are not limited to, the mean fluorescence associated with individual fluorescent antibody-detected cell surface molecules or cytokines, or the average fluorescence intensity, the median fluorescence intensity, the variance in fluorescence intensity, or some relationship among these.

In some aspects of embodiments with analytical steps involving flow cytometry, minimal parameters or characteristics of the beads are scatter (FS and/or SS) and at least one fluorescent wavelengths. Flow cytometry can be used to quantitate parameters such as the presence of cell surface proteins or conformational or posttranslational modification thereof; intracellular or secreted protein, where permeabilization allows antibody (or probe) access, and the like. Flow cytometry methods are known in the art, and described in the following: Flow Cytometry and Cell Storing (Springer Lab Manual), Radbruch, Ed., Springer Verlag, 2000; Ormerod, Flow Cytometry, Springer Verlag, 1999; Flow Cytometry Protocols (Methods in Molecular Biology, No 91), Jaroszeski and Heller, Eds., Humana Press, 1998; Current Protocols in Cytometry, Robinson et al., eds, John Wiley & Sons, New York, N.Y., 2000.

The staining intensity of cells may be monitored by flow cytometry, where lasers detect the quantitative levels of fluorochrome (which is proportional to the amount of cell surface marker bound by specific reagents, e.g. antibodies). Flow cytometry, or FACS, may also be used to separate cell populations based on the intensity of binding to a specific reagent, as well as other parameters such as cell size and light scatter. Although the absolute level of staining can differ with a particular fluorochrome and reagent preparation, the data can be normalized to a control. In order to normalize the distribution to a control, each cell is recorded as a data point having a particular intensity of staining.

In order to normalize the distribution to a control, each cell is recorded as a data point having a particular intensity of staining. These data points may be displayed according to a log scale, where the unit of measure is arbitrary staining intensity. In one example, the brightest cells in a population are designated as 4 logs more intense than the cells having the lowest level of staining. When displayed in this manner, it is clear that the cells falling in the highest log of staining intensity are bright, while those in the lowest intensity are negative. The “low” staining cells, which fall in the 2-3 log of staining intensity, may have properties that are unique from the negative and positive cells. An alternative control may utilize a substrate having a defined density of marker on its surface, for example a fabricated bead or cell line, which provides the positive control for intensity. The “low” designation indicates that the level of staining is above the brightness of an isotype matched control, but is not as intense as the most brightly staining cells normally found in the population.

The readouts of selected parameters are capable of being read simultaneously, or in sequence during a single analysis, as for example through the use of fluorescent antibodies to cell surface molecules. As an example, these can be tagged with different fluorochromes, fluorescent bead, tags, e.g. quantum dots, etc., allowing analysis of up to 4 or more fluorescent colors simultaneously by flow cytometry. For example, a negative designation indicates that the level of staining is at or below the brightness of an isotype matched negative control; whereas a dim designation indicates that the level of staining can be near the level of a negative stain, but can also be brighter than an isotype matched control.

Identifiers of individual cells, for example different cell types or cell type variants, may be fluorescent, as for example labeling of different unit cell types with different levels of a fluorescent compound, and the like as described herein above. In some aspects of embodiments where two cell types are to be mixed, one is labeled and the other not. In some aspects of embodiments where three or more cell types are to be included, each cell type may labeled to different levels of fluorescence by incubation with different concentrations of a labeling compound, or for different times. As identifiers of large numbers of cells, a matrix of fluorescence labeling intensities of two or more different fluorescent colors may be used, such that the number of distinct unit cell types that are identified is a number of fluorescent levels of one color, e.g., carboxyfluorescein succinimidyl ester (CFSE), times the number of fluorescence levels employed of the second color, e.g. tetramethylrhodamine isothiocyanate (TRITC), or the like, times the number of levels of a third color, etc. Alternatively, intrinsic light scattering properties of the different cell types, or characteristics of the BioMAPs of the test parameters included in the analysis, may be used in addition to or in place of fluorescent labels as unit cell type identifiers.

In another aspect, cells may be enriched, depleted, separated, sorted and/or purified using conventional affinity or antibody techniques. For example, the ligand and/or antibody may be conjugated with labels to allow for ease of separation of the particular cell type, e.g. magnetic beads; biotin, which binds with high affinity to avidin or streptavidin; fluorochromes, which can be used with a fluorescence activated cell sorter; haptens; and the like.

In one embodiment, the ligand, agent, and/or antibodies described herein may be directly or indirectly conjugated to a magnetic reagent, such as a super-paramagnetic microparticle (microparticle). Direct conjugation to a magnetic particle may be achieved by use of various chemical linking groups, as known in the art. In some embodiments, the antibody is coupled to the microparticles through side chain amino or sulfhydryl groups and heterofunctional cross-linking reagents.

A large number of heterofunctional compounds are available for linking to entities. For example, at least, 3-(2-pyridyidithio)propionic acid N-hydroxysuccinimide ester (SPDP) or 4-(N-maleimidomethyl)-cyclohexane-1-carboxylic acid N-hydroxysuccinimide ester (SMCC) with a reactive sulfhydryl group on the antibody and a reactive amino group on the magnetic particle can be used. An example of a magnetic separation device is described in WO 90/07380, PCT/US96/00953, and EP 438,520, incorporated herein by reference in its entirety.

The purified cell population may be collected in any appropriate medium. Suitable media may include, for example, Dulbecco's Modified Eagle Medium (dMEM), Hank's Basic Salt Solution (HBSS), Dulbecco's phosphate buffered saline (dPBS), RPMI, Iscove's modified Dulbecco's medium (IMDM), phosphate buffered saline (PBS) with 5 mM EDTA, etc., frequently supplemented with fetal calf serum (FCS), bovine serum albumin (BSA), human serum albumin (HSA), and StemPro®hESC SFM.

In one embodiment, the cells expressing markers characteristic of the pancreatic endocrine lineage are enriched by treatment with at least one agent that selects cells that do not express markers characteristic of the pancreatic endocrine lineage. In an alternate embodiment, the cells expressing markers characteristic of the pancreatic endocrine lineage are enriched by treatment with at least one agent that selects for insulin-producing cells.

Using the methods described herein, cell populations or cell cultures may be enriched in cell content by at least about 2- to about 1000-fold as compared to untreated cell populations or cell cultures. In some embodiments, cells expressing markers characteristic of the pancreatic endocrine lineage may be enriched by at least about 5- to about 500-fold as compared to untreated cell populations or cell cultures. In other embodiments, cells expressing markers characteristic of the pancreatic endocrine lineage may be enriched from at least about 10- to about 200-fold as compared to untreated cell populations or cell cultures. In still other embodiments, cells expressing markers characteristic of the pancreatic endocrine lineage may be enriched from at least about 20- to about 100-fold as compared to untreated cell populations or cell cultures. In yet other embodiments, cells expressing markers characteristic of the pancreatic endocrine lineage may be enriched from at least about 40- to about 80-fold as compared to untreated cell populations or cell cultures. In certain embodiments, cells expressing markers characteristic of the pancreatic endocrine lineage may be enriched from at least about 2- to about 20-fold as compared to untreated cell populations or cell cultures.

Characterization of Cells Derived from Pluripotent Stem Cells

The formation of differentiated cells from pluripotent stem cells may be determined by determining the expression of markers characteristic of a given differentiated cell type. In some embodiments, the identification and characterization of a differentiated cell is by expression of a certain marker or different expression levels and patterns of more than one marker.

Specifically, the presence or absence, the high or low expression, of one or more the marker(s) can typify and identify a cell-type. Also, certain markers may have transient expression, whereby the marker is highly expressed during one stage of development and poorly expressed in another stage of development. The expression of certain markers can be determined by measuring the level at which the marker is present in the cells of the cell culture or cell population as compared to a standardized or normalized control marker. In such processes, the measurement of marker expression can be qualitative or quantitative. One method of quantitating the expression of markers that are produced by marker genes is through the use of quantitative PCR (Q-PCR). Methods of performing Q-PCR are well known in the art. Other methods which are known in the art can also be used to quantitate marker gene expression. For example, the expression of a marker gene product can be detected by using antibodies specific for the marker gene product of interest (e.g. Western blot, flow cytometry analysis, and the like). In certain embodiments, the expression of marker genes characteristic of differentiated cells as well as the lack of significant expression of marker genes characteristic of differentiated cells may be determined.

The expression of tissue-specific gene products can also be detected at the mRNA level by Northern blot analysis, dot-blot hybridization analysis, or by reverse transcriptase initiated polymerase chain reaction (RT-PCR) using sequence-specific primers in standard amplification methods. See U.S. Pat. No. 5,843,780 for further details. Sequence data for particular markers listed in this disclosure can be obtained from public databases such as GenBank.

Pluripotent stem cells may express one or more of the stage-specific embryonic antigens (SSEA) 3 and 4, and markers detectable using antibodies designated Tra-1-60 and Tra-1-81 (Thomson et al., Science 282:1145, 1998). Differentiation of pluripotent stem cells in vitro results in the loss of SSEA-4, Tra 1-60, and Tra 1-81 expression (if present) and increased expression of SSEA-1. Undifferentiated pluripotent stem cells typically have alkaline phosphatase activity, which can be detected by fixing the cells with 4% paraformaldehyde, and then developing with Vector Red as a substrate, as described by the manufacturer (Vector Laboratories, Burlingame Calif.). Undifferentiated pluripotent stem cells also typically express OCT4 and TERT, as detected by RT-PCR.

Markers characteristic of the pancreatic endoderm lineage are selected from the group consisting of PDX1, HNF1 beta, PTF1 alpha, HNF6, HB9 and PROX1. Suitable for use in the present invention is a cell that expresses at least one of the markers characteristic of the pancreatic endoderm lineage. In one aspect of the present invention, a cell expressing markers characteristic of the pancreatic endoderm lineage is a pancreatic endoderm cell.

Markers characteristic of the definitive endoderm lineage are selected from the group consisting of SOX17, GATA4, HNF3 beta, GSC, CER1, Nodal, FGF8, Brachyury, Mix-like homeobox protein, FGF4, CD48, eomesodermin (EOMES), DKK4, FGF17, GATA6, CD184, C-Kit, CD99, and OTX2. Suitable for use in the present invention is a cell that expresses at least one of the markers characteristic of the definitive endoderm lineage. In one aspect of the present invention, a cell expressing markers characteristic of the definitive endoderm lineage is a primitive streak precursor cell. In an alternate aspect, a cell expressing markers characteristic of the definitive endoderm lineage is a mesendoderm cell. In an alternate aspect, a cell expressing markers characteristic of the definitive endoderm lineage is a definitive endoderm cell.

Markers characteristic of the pancreatic endocrine lineage are selected from the group consisting of NGN3, NEUROD, ISL1, PDX1, NKX6.1, PAX4, NGN3, and PTF-1 alpha. In one embodiment, a pancreatic endocrine cell is capable of expressing at least one of the following hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide. Suitable for use in the present invention is a cell that expresses at least one of the markers characteristic of the pancreatic endocrine lineage. In one aspect of the present invention, a cell expressing markers characteristic of the pancreatic endocrine lineage is a pancreatic endocrine cell. The pancreatic endocrine cell may be a pancreatic hormone-expressing cell. Alternatively, the pancreatic endocrine cell may be a pancreatic hormone-secreting cell.

In one aspect of the present invention, the pancreatic endocrine cell is a cell expressing markers characteristic of the β cell lineage. A cell expressing markers characteristic of the β cell lineage expresses PDX1 and at least one of the following transcription factors: NGN3, NKX2.2, NKX6.1, NEUROD, ISL1, HNF3 beta, MAFA, PAX4, and PAX6. In one aspect of the present invention, a cell expressing markers characteristic of the β cell lineage is a β cell.

Pluripotent Stem Cells Characterization of Pluripotent Stem Cells

Pluripotent stem cells may express one or more of the stage-specific embryonic antigens (SSEA) 3 and 4, and markers detectable using antibodies designated Tra-1-60 and Tra-1-81 (Thomson et al., Science 282:1145 1998). Differentiation of pluripotent stem cells in vitro results in the loss of SSEA-4, Tra-1-60, and Tra-1-81 expression (if present) and increased expression of SSEA-1. Undifferentiated pluripotent stem cells typically have alkaline phosphatase activity, which can be detected by fixing the cells with 4% paraformaldehyde and then developing with Vector Red as a substrate, as described by the manufacturer (Vector Laboratories, Burlingame Calif.). Undifferentiated pluripotent stem cells also typically express Oct-4 and TERT, as detected by RT-PCR.

Another desirable phenotype of propagated pluripotent stem cells is a potential to differentiate into cells of all three germinal layers: endoderm, mesoderm, and ectoderm tissues. Pluripotency of stem cells can be confirmed, for example, by injecting cells into severe combined immunodeficient (SCID) mice, fixing the teratomas that form using 4% paraformaldehyde, and then examining them histologically for evidence of cell types from the three germ layers. Alternatively, pluripotency may be determined by the creation of embryoid bodies and assessing the embryoid bodies for the presence of markers associated with the three germinal layers.

Propagated pluripotent stem cell lines may be karyotyped using a standard G-banding technique and compared to published karyotypes of the corresponding primate species. It is desirable to obtain cells that have a “normal karyotype,” which means that the cells are euploid, wherein all human chromosomes are present and not noticeably altered.

Sources of Pluripotent Stem Cells

The types of pluripotent stem cells that may be used include established lines of pluripotent cells derived from tissue formed after gestation, including pre-embryonic tissue (such as, for example, a blastocyst), embryonic tissue, or fetal tissue taken any time during gestation, typically but not necessarily before approximately 10-12 weeks gestation. Non-limiting examples are established lines of human embryonic stem cells or human embryonic germ cells, such as, for example the human embryonic stem cell lines H1, H7, and H9 (WiCell). Also contemplated is use of the compositions of this disclosure during the initial establishment or stabilization of such cells, in which case the source cells would be primary pluripotent cells taken directly from the source tissues. Also suitable are cells taken from a pluripotent stem cell population already cultured in the absence of feeder cells, as well as a pluripotent stem cell population already cultured in the presence of feeder cells. Also suitable are mutant human embryonic stem cell lines, such as, for example, BG01v (BresaGen, Athens, Ga.). Also suitable are cells derived from adult human somatic cells, such as, for examples, cells disclosed in Takahashi et al, Cell 131: 1-12 (2007).

In one embodiment, human embryonic stem cells are prepared as described by Thomson et al. (U.S. Pat. No. 5,843,780; Science 282:1145, 1998; Curr. Top. Dev. Biol. 38:133 ff., 1998; Proc. Natl. Acad. Sci. U.S.A. 92:7844, 1995).

Also contemplated, are pluripotent stem cells that are derived from somatic cells. In one embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Takahashi et al. (Cell 126: 663-676, 2006).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Li et al. (Cell Stem Cell 4: 16-19, 2009).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Maherali et al. (Cell Stem Cell 1: 55-70, 2007).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Stadtfeld et al. (Cell Stem Cell 2: 230-240).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Nakagawa et al. (Nature Biotechnology 26: 101-106, 2008).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in Takahashi et al. (Cell 131: 861-872, 2007).

In an alternate embodiment, pluripotent stem cells suitable for use in the present invention may be derived according to the methods described in U.S. patent application Ser. No. 61/256,149, assigned to Centocor R&D, Inc.

Culture of Pluripotent Stem Cells

In one embodiment, pluripotent stem cells are cultured on a layer of feeder cells or extracellular matrix protein that support the pluripotent stem cells in various ways, prior to culturing according to the methods of the present invention. For example, pluripotent stem cells are cultured on a feeder cell layer that supports proliferation of pluripotent stem cells without undergoing substantial differentiation. The growth of pluripotent stem cells on a feeder cell layer without differentiation is supported using (i) Obtaining a culture vessel containing a feeder cell layer; and (ii) a medium conditioned by culturing previously with another cell type, or a non-conditioned medium, for example, free of serum or even chemically defined.

In another example, pluripotent stem cells are cultured in a culture system that is essentially free of feeder cells, but nonetheless supports proliferation of pluripotent stem cells without undergoing substantial differentiation. The growth of pluripotent stem cells in feeder-cell free culture without differentiation is supported using (i) an adlayer on a solid substrate surface with one or more extracellular matrix proteins; and (ii) a medium conditioned by culturing previously with another cell type, or a non-conditioned medium, for example, free of serum or even chemically defined.

In an alternate embodiment, pluripotent stem cells are cultured on a surface modified plate containing from at least about 0.5% N, a sum of O and N of greater than or equal to 17.2% and a contact angle of at least about 13.9 degrees in a medium conditioned by culturing previously with another cell type, or a non-conditioned medium, for example, free of serum or even chemically defined.

Culture medium: An example of cell culture medium suitable for use in the present invention may be found in US20020072117. Another example of cell culture medium suitable for use in the present invention may be found in U.S. Pat. No. 6,642,048. Another example of cell culture medium suitable for use in the present invention may be found in WO2005014799. Another example of cell culture medium suitable for use in the present invention may be found in Xu et al. (Stem Cells 22: 972-980, 2004). Another example of cell culture medium suitable for use in the present invention may be found in US20070010011. Another example of cell culture medium suitable for use in the present invention may be found in Cheon et al. (BioReprod DOI:10.1095/biolreprod.105.046870; 19 Oct. 2005). Another example of cell culture medium suitable for use in the present invention may be found in Levenstein et al. (Stem Cells 24: 568-574, 2006). Another example of cell culture medium suitable for use in the present invention may be found in US20050148070. Another example of cell culture medium suitable for use in the present invention may be found in US20050233446. Another example of cell culture medium suitable for use in the present invention may be found in U.S. Pat. No. 6,800,480. Another example of cell culture medium suitable for use in the present invention may be found in US20050244962. Another example of cell culture medium suitable for use in the present invention may be found in WO2005065354. Another example of cell culture medium suitable for use in the present invention may be found in WO2005086845.

Suitable culture media may also be made from the following components, such as, for example, Dulbecco's modified Eagle's medium (DMEM), Gibco #11965-092; Knockout Dulbecco's modified Eagle's medium (KO DMEM), Gibco #10829-018; Ham's F12/50% DMEM basal medium; 200 mM L-glutamine, Gibco #15039-027; non-essential amino acid solution, Gibco 11140-050; β-mercaptoethanol, Sigma # M7522; human recombinant basic fibroblast growth factor (bFGF), Gibco #13256-029.

Differentiation of Pluripotent Stem Cells

In one embodiment, pluripotent stem cells are propagated in culture and then treated in a manner that promotes their differentiation into another cell type. For example, pluripotent stem cells formed using the methods of the present invention may be differentiated into neural progenitors or cardiomyocytes according to the methods disclosed in WO2007030870.

In another example, pluripotent stem cells formed using the methods of the present invention may be differentiated into hepatocytes according to the methods disclosed in U.S. Pat. No. 6,458,589.

Differentiation of Pluripotent Stem Cells Formed Using the Methods of the Present Invention into Cells Expressing Markers Characteristic of the Definitive Endoderm Lineage

Pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage by any method in the art.

For example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in D'Amour et al, Nature Biotechnology 23, 1534-1541 (2005).

For example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in Shinozaki et al, Development 131, 1651-1662 (2004).

For example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in McLean et al, Stem Cells 25, 29-38 (2007).

For example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in D'Amour et al, Nature Biotechnology 24, 1392-1401 (2006).

In another example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in U.S. patent application Ser. No. 11/736,908, assigned to LifeScan, Inc.

In another example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in U.S. patent application Ser. No. 11/779,311, assigned to LifeScan, Inc.

In another example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in U.S. patent application Ser. No. 12/493,741, assigned to LifeScan, Inc.

In another example, pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the definitive endoderm lineage according to the methods disclosed in U.S. patent application Ser. No. 12/494,789, assigned to LifeScan, Inc.

Formation of cells expressing markers characteristic of the definitive endoderm lineage may be determined by testing for the presence of the markers before and after following a particular protocol. Pluripotent stem cells typically do not express such markers. Thus, differentiation of pluripotent cells is detected when cells begin to express them.

Differentiation of Pluripotent Stem Cells Formed Using the Methods of the Present Invention into Cells Expressing Markers Characteristic of the Pancreatic Endoderm Lineage

Pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the pancreatic endoderm lineage by any method in the art.

For example, pluripotent stem cells may be differentiated into cells expressing markers characteristic of the pancreatic endoderm lineage according to the methods disclosed in D'Amour et al, Nature Biotechnology 24, 1392-1401 (2006).

For example, cells expressing markers characteristic of the definitive endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endoderm lineage, by treating the cells expressing markers characteristic of the definitive endoderm lineage with a fibroblast growth factor and the hedgehog signaling pathway inhibitor KAAD-cyclopamine, then removing the medium containing the fibroblast growth factor and KAAD-cyclopamine and subsequently culturing the cells in medium containing retinoic acid, a fibroblast growth factor and KAAD-cyclopamine. An example of this method is disclosed in Nature Biotechnology 24, 1392-1401 (2006).

For example, cells expressing markers characteristic of the definitive endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endoderm lineage, by treating the cells expressing markers characteristic of the definitive endoderm lineage with retinoic acid one fibroblast growth factor for a period of time, according to the methods disclosed in U.S. patent application Ser. No. 11/736,908, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the definitive endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endoderm lineage, by treating the cells expressing markers characteristic of the definitive endoderm lineage with retinoic acid (Sigma-Aldrich, MO) and exendin 4, then removing the medium containing DAPT (Sigma-Aldrich, MO) and exendin 4 and subsequently culturing the cells in medium containing exendin 1, IGF-1 and HGF. An example of this method is disclosed in Nature Biotechnology 24, 1392-1401 (2006).

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing exendin 4, then removing the medium containing exendin 4 and subsequently culturing the cells in medium containing exendin 1, IGF-1 and HGF. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing DAPT (Sigma-Aldrich, MO) and exendin 4. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing exendin 4. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 11/736,908, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 11/779,311, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 60/953,178, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 60/990,529, assigned to LifeScan, Inc.

Differentiation of Pluripotent Stem Cells Formed Using the Methods of the Present Invention into Cells Expressing Markers Characteristic of the Pancreatic Endocrine Lineage

Pluripotent stem cells formed using the methods of the present invention may be differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage by any method in the art.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing exendin 4, then removing the medium containing exendin 4 and subsequently culturing the cells in medium containing exendin 1, IGF-1 and HGF. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing DAPT (Sigma-Aldrich, MO) and exendin 4. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by culturing the cells expressing markers characteristic of the pancreatic endoderm lineage in medium containing exendin 4. An example of this method is disclosed in D'Amour et al, Nature Biotechnology, 2006.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 11/736,908, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 11/779,311, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 60/953,178, assigned to LifeScan, Inc.

For example, cells expressing markers characteristic of the pancreatic endoderm lineage obtained according to the methods of the present invention are further differentiated into cells expressing markers characteristic of the pancreatic endocrine lineage, by treating the cells expressing markers characteristic of the pancreatic endoderm lineage with a factor that inhibits the Notch signaling pathway, according to the methods disclosed in U.S. patent application Ser. No. 60/990,529, assigned to LifeScan, Inc.

The present invention is further illustrated, but not limited by, the following examples.

EXAMPLES Example 1 Differentiation of Human Embryonic Stem Cells of the Cell Line H1 to Pancreatic Endocrine Cells in the Absence of Fetal Bovine Serum

Cells of the human embryonic stem cells line H1 at various passages (p40 to p52) were cultured on MATRIGEL (1:30 dilution) coated dishes and differentiated into pancreatic lineages using a multi-step protocol as follows:

-   -   a. Stage I (Definitive Endoderm): Human embryonic stem cells         were cultured in RPMI medium supplemented with 2% fatty         acid-free BSA (Catalog#68700, Proliant, IA), and 100 ng/ml         activin A (R&D Systems, MN) plus 20 ng/ml WNT-3a         (Catalog#1324-WN-002, R&D Systems, MN) plus 8 ng/ml of bFGF         (Catalog#100-18B, PeproTech, NJ), for one day. Cells were then         treated with RPMI medium supplemented with 2% BSA and 100 ng/ml         activin A plus 8 ng/ml of bFGF for an additional two days, then     -   b. Stage II (Primitive gut tube): Cells were treated with         RPMI+2% fatty acid-free BSA and 50 ng/ml FGF7 and 0.25 μM SANT-1         (#S4572, Sigma, MO), for two to three days, then     -   c. Stage III (Posterior foregut): Cells were treated with         DMEM/High-Glucose supplemented with 1:200 dilution of ITS-X         (Invitrogen, CA) and 0.1% BSA (Lipid Rich) (Invitrogen, Ca No.         11021-045), 50 ng/ml FGF7, 0.25 μM SANT-1, 2 μM Retinoic acid         (RA) (Sigma, MO), 100 ng/ml of Noggin (R & D Systems, MN), and         Activin A at 20 ng/ml for four days; In certain variations,         Noggin was replaced with the AMPK inhibitor         6-[4-(2-Piperidin-1-ylethoxy)phenyl]-3-pyridin-4-ylpyrazolo[1,5-a]pyrimidine         (Sigma, No. P5499) at a concentration of 2 μM. In yet other         variations, a P38 inhibitor         (4-[4-(4-Fluorophenyl)-1-(3-phenylpropyl)-5-pyridin-4-yl-1H-imidazol-2-yl]but-3-yn-1-ol)         (disclosed in U.S. Pat. No. 6,521,655) was added at 2.5 μM, then     -   d. Stage IV (Pancreatic endocrine precursor): Cells were treated         with DMEM/High-Glucose supplemented with 1:200 dilution of ITS-X         (Invitrogen, CA) and 0.1% BSA (Invitrogen, Ca), 100 ng/ml         Noggin, 1 μM ALK5 inhibitor (SD-208, disclosed in Molecular         Pharmacology 2007 72:152-161) for three days, then     -   e. Stage V (Pancreatic endocrine cells): Cell were treated with         DMEM/High-Glucose supplemented with 1:200 dilution of ITS-X         (Invitrogen, CA), 0.1% BSA (Invitrogen, Ca), 1 μM ALK5 inhibitor         II (Catalog#616452, Calbiochem, Ca) for seven days, then     -   f. Stage VI (Mature Pancreatic endocrine cells): Cells were         treated with DMEM/High-Glucose supplemented with 1:200 dilution         of ITS-X (Invitrogen, CA), 0.1% BSA (Invitrogen, Ca) for seven         days, with media changes every other day.

Example 2 Flow Cytometric Characterization and Sorting of Enriched Various Pancreatic Cell Lineages

To facilitate the isolation and characterization of novel cell populations form various stages of the differentiation process outlined in Example 1, a detailed characterization of the cells obtained from the various stages was done by flow cytometry. A complete list of antibodies used and the expression levels of surface markers at various stages of differentiation is shown in Table I.

Cells of the human embryonic stem cell line H1 at various passages (p40 to p52) were cultured on MATRIGEL-coated plates, and differentiated into pancreatic endocrine cells using the protocol described in Example 1.

Cells at different stages of maturation (posterior foregut (Stage III), endocrine precursor cells (Stage IV), pancreatic endocrine cells (Stage V) or mature pancreatic endocrine cells (Stage VI) were gently released by incubation in TrypLE Express (Invitrogen #12604, CA) for 2-3 minutes at 37° C. and washed twice in BD FACS staining buffer containing 2% BSA (BD #554657, CA). Approximately 0.5-1×10⁶ cells were re-suspended in 100-200 μl blocking buffer (0.5% human gamma-globulin diluted 1:4 in staining buffer (BD, CA) for staining. For staining with directly conjugated primary antibodies, the appropriate antibody was added to the cells at a final dilution of 1:20, and cells and incubated for 30 min at 4° C. For unconjugated antibodies, primary antibodies were added to cells at 1:50-1:100 dilution and cells incubated for 30 min at 4° C. followed two washes in staining buffer. Cells were then incubated in the appropriate secondary antibodies at 1:500 dilution. Stained cells were re-suspended in 300 μl staining buffer and 5-10 μl of 7AAD added for live/dead cell discrimination prior to analysis on the BD FACS Canto II.

For cell sorting, approximately 30-40 million cells were similarly processed as for flow cytometric analysis. Cells were stained with the appropriate antibodies as shown in Table II. Cells were sorted either into two or three sub-populations as summarized in Table II. Cell sorting gates were established based on the isotype matched controls. An aliquot of sorted cells were analyzed for purity following the sorting followed by PCR analysis for expression of key pancreatic markers. RNA was collected using the Rneasy Mini Kit, Qiagen, CA) was collected from presort sample, and the various fractions.

Cell surface markers used for sorting were selected based on the expression of various markers in populations of cells analyzed at different stages of the differentiation protocol outlined in Example 1. The markers employed in this study are disclosed in Table II. Briefly, the surface markers disclosed in Table II were used either singly or in combination to sort various populations of cells. Samples of the sorted cells were taken to analyze the expression of markers characteristic of the pancreatic endocrine lineage by real-time PCR.

Sorting of Cells Expressing Markers Characteristic of the Pancreatic Endocrine Lineage

Antibodies to CD56 and CD13 were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. Three populations of cells were identified: a) CD56⁺CD13⁻, b) CD56⁻CD13⁻ and c) CD56⁻CD13⁺ populations of cells. The CD56⁺CD13⁻ population was enriched approximately 1.3 fold following sorting, and the sorted cells were highly enriched for the expression of markers characteristic of the pancreatic endocrine lineage, including NEUROD, NGN3, PDX1, NKX6.1, NKX2.2 and PAX-4, when compared to unsorted cells at stage IV, or populations of CD56⁻CD13⁻ cells, or populations of CD56⁻CD13⁺ cells. See FIG. 1, panels a-f.

In a second series of experiments, antibodies to CD133 were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD133⁺, and b) CD133⁻ populations of cells. The CD133⁻ population was enriched approximately 1.9 fold following sorting, and the sorted cells were highly enriched for the expression of markers characteristic of the pancreatic endocrine lineage, including NEUROD, NGN3, PDX1, NKX6.1, NKX2.2 and PAX-4, when compared to unsorted cells at stage IV, or populations of CD133⁺ cells. See FIG. 2, panels a-f.

In a third series of experiments, antibodies to CD49c were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD49c^(HI), and b) CD49c^(LO) populations of cells. CD49c^(LO) cells were enriched approximately 3.1 fold following sorting, and the sorted cells were highly enriched for the expression of markers characteristic of the pancreatic endocrine lineage, including NEUROD, NGN3, PDX1, and NKX6.1 when compared to unsorted cells or CD49c^(HI) cells. See FIG. 3, panels a-d.

In a fourth series of experiments, antibodies to CD56 and CD15 were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. The following populations of cells were identified: a) CD56⁺CD15^(LO), b) CD56⁺CD15^(HI), c) CD15⁺ and d) CD15⁻ populations of cells. Populations of CD15⁻ cells were enriched approximately 1.1 fold following sorting. Populations of CD56⁺CD15^(lo) cells were highly enriched for the expression of markers characteristic of the pancreatic endocrine lineage including NEUROD, NGN3, PDX1, NKX6.1, Insulin and glucagon compared to unsorted cells, or populations of CD56⁺CD15^(hi) cells. See FIG. 4, panels a-f. Similarly, populations of CD15⁻ cells sorted using a single marker were highly enriched for the expression of markers characteristic of the pancreatic endocrine lineage including NEUROD, NGN3, PDX1, NKX6.1, NKX2.2, PAX-4, glucagon and insulin, when compared to unsorted cells or populations of CD15⁺ cells. See FIG. 5, panels a-h.

In a fifth series of experiments, antibodies to CD56 and CD57 were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD56⁺CD57⁺, and b) CD56⁺CD57⁻ populations of cells. Populations of CD56⁺CD57⁺ cells were enriched approximately 1.9 fold following sorting. CD56⁺CD57⁺ cells were highly enriched for the expression of markers characteristic of the pancreatic endoderm lineage, including NEUROD, NGN3, PDX1, NKX6.1, NKX2.2, as wells as insulin and glucagon, when compared to unsorted cells or populations of CD56⁺CD57⁻ cells. See FIG. 6, panel a-g. Similar results were observed when populations of cells at Stage V of the differentiation protocol outlined in Example 1 were sorted using antibodies to CD56 and CD57.

In a sixth series of experiments, antibodies to CD56 and CD184 were used to sort a population of cells obtained from Stage IV of the differentiation protocol outlined in Example 1. Three populations of cells were identified: a) CD184⁺, b) CD184⁻, and c) CD56⁺CD184⁻ populations of cells. Table IV summarizes the expression of CD184 in cells before and after the enrichment. Populations of CD184⁺ cells were enriched for the expression of markers characteristic of the pancreatic endocrine lineage, including PAX4, NEUROD, NKX6.1, PDX1 and PTF1 alpha. The expression of ZIC1, Albumin and CDX2 was decreased. See FIG. 7, panels a-i.

Sorting of Insulin Producing Cells

Antibodies to CD98 were used to sort a population of cells obtained from Stage VI of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD98^(+(Hi)), and b) CD98^(−(Lo)) populations of cells. Populations of CD98^(+(Hi)) cells were enriched approximately 1.6 fold following sorting. CD98^(+(Hi)) cells were enriched for the expression of NEUROD, NGN3, insulin, and glucagon. See FIG. 8, panels a-d.

In another series of experiments, antibodies to CD47 were used to sort a population of cells obtained from Stage V of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD47^(Hi(+)), and b) CD47^(Lo(−)) populations of cells. CD47^(LO(−)) cells were enriched approximately 3.3 fold following sorting. CD47^(Lo(−)) cells were enriched for the expression of NEUROD, NGN3, PDX1, NKX6.1, NKX2.2 and PAX4. See FIG. 9, panels a-f.

In another series of experiments, antibodies to CD47 were used to sort a population of cells obtained from Stage VI of the differentiation protocol outlined in Example 1. Two populations of cells were identified: a) CD47^(Hi(+)), and b) CD47^(LO(−)) populations of cells. CD47^(Lo(−)) cells were enriched for the expression of PDX-1, NKX6.1, NKX2.2, PAX-4, PTF1a, NGN3, Insulin and Glucagon. See FIG. 10, panels a-h.

Example 3 Sorting of Lif Receptor Positive Cells at Primitive Gut Tube Stage (Stage 2)

Cells of the human embryonic stem cell line H1 at passage 44 were cultured on MATRIGEL-coated plates, and differentiated into insulin producing cells using the following protocol:

-   -   a. RPMI medium supplemented with 2% fatty acid-free BSA         (Catalog#68700, Proliant, IA), and 100 ng/ml activin A (R&D         Systems, MN) plus 20 ng/ml WNT-3a (Catalog#1324-WN-002, R&D         Systems, MN) plus 8 ng/ml of bFGF (Catalog#100-18B, PeproTech,         NJ), for one day followed by treatment with RPMI media         supplemented with 2% BSA and 100 ng/ml activin A plus 8 ng/ml of         bFGF for an additional two days (Stage 1), then     -   b. RPMI+2% BSA+50 ng/ml FGF7+0.25 μM SANT-1 (#S4572, Sigma, MO),         for three days (Stage 2), then     -   c. DMEM/High-Glucose+1:200 dilution of ITS-X (Invitrogen,         CA)+0.1% BSA (Invitrogen, Ca) 50 ng/ml FGF7 (Peprotech, NJ)+0.25         μM SANT-1+2 μM Retinoic acid (RA) (Sigma, MO)+100 ng/ml of         Noggin (R & D Systems, MN) and 20 ng/ml of activin A for four         days (Stage 3), then     -   d. DMEM/High-Glucose+1:200 dilution of ITS-X (Invitrogen,         CA)+0.1% BSA (Invitrogen, Ca)+100 ng/ml Noggin+1 μM ALK5         inhibitor (SCIO120)+ for three days (Stage 4)

Stage 2 cells were dispersed into single cells using TrypLE Express (Invitrogen, Carlsbad, Calif.) and washed in stage 4 basal media (DM-Hg+ITS-X+BSA). Released cells were spun and the resulting cell pellet suspended in a staining buffer consisting of 2% BSA, 0.05% sodium azide in PBS (Sigma, MO). As appropriate, the cells were Fc-receptor blocked for 15 minutes using a 0.1% γ-globulin (Sigma) solution. Aliquots (approximately 10⁵ cells) were incubated with Lif receptor-Phycoerythrin (PE) (R & D Systems, MN) conjugated monoclonal antibodies (5 μl antibody per 10⁶ cells). Controls included appropriate isotype matched antibodies and unstained cells. All incubations with antibodies were performed for 30 mins at 4° C. after which the cells were washed with the staining buffer. Stained cells were sorted on a FACS Aria (BD, Ca). RNA (Rneasy Mini Kit, Qiagen, CA) was collected from presort sample, Lif receptor+fraction and Lif receptor negative fraction. The Lif receptor expression level and pattern is summarized in Table III.

Table III summarizes the expression of Lif receptor at days 2 and 3 of stage 2. By day 3 of stage 2, approximately 70% of the cells expressed Lif receptor. As summarized in Table III, high expression of Lif receptor was unique to stage 2 cells, as stage 3 and 4 cells showed minimal expression of Lif receptor. As shown in FIG. 11, panels a-b, stage 2 cells enriched for the Lif receptor showed a significant increase in expression of HNF4 alpha as compared to unsorted cells or Lif receptor negative cells. Expression of Lif receptor mRNA as measured by real-time PCR was also enhanced in cell fraction containing Lif-receptor positive cells.

Example 4 Magnetic Bead Sorting for Cells for the Depletion of SSEA-4+ Cells to Reduce Tumor Formation In Vivo

Expression of the SSEA4antigen is a key indicator of pluripotency in human embryonic stem cells, and expression of this marker is greatly down regulated during the differentiation process. However, residual SSEA-4 positive cells may be responsible for tumors and/or teratomas that are observed following transplantation of partially differentiated cells. To reduce teratoma formation, methods were developed to deplete contaminating SSEA4⁺ cells from differentiated cells prior to transplantation.

Cells of the human embryonic stem cell line H1 (passage 40-52) were differentiated to various stages of the differentiation protocol outlined in Example 1. In order to test proof of concept and efficacy of SSEA-4 depletion, this study was first done with cells differentiated only to the primitive gut tube stage (Stage 2 in the differentiation protocol outlined in Example 1) in order to ensure cells still retained higher levels of SSEA-4 expression. In subsequent experiments, cells expressing SSEA-4 were depleted in populations of cells differentiated at Stage 4 of the differentiation protocol outline in Example 1. See Table V for the results observed. Cells were gently released into single cells by incubation in TrypLE Express (Invitrogen #12604, CA) for 2-3 minutes at 37° C. To enhance cell survival and viability during depletion, anti-apoptotic agents including 10 μM Y-27632 (Cat # Y 0503, Sigma, St Louis Mo.) or 0.5 μM Thiazovivin (Cat #04-0017, Stemgent, San Diego, Calif.) were added to the cells prior to collection and in all isolation buffers.

Cells were washed in Isolation Buffer containing Ca²⁺ and Mg²⁺ free phosphate buffered saline (PBS) supplemented with 0.1% BSA and 2 mM EDTA. Between 10-100×10⁶ cells were re-suspended in isolation buffer a final cell density of 5×10⁶ cells per 500 μl. Twenty five μl SSEA-4 antibody was added per 500 μl of cells and cells incubated for 15-20 minutes at room temperature on a gentle rocker to ensure continuous mixing. Cells were washed in isolation buffer by spinning at 300×g for 8 min. Supernatant was removed and cells re-suspended in original buffer volume and 50 μl of prewashed SSEA-4 Depletion beads (DynaBeads® SSEA-4, Invitrogen, #11160D) added for every 500 μl of cell suspension. Cells and beads were mixed and incubated for 15-20 minutes at room temperature with continuous gentle tilting and rotation. Cells were mixed by gentle pipetting and placed on a magnet for 5 min. The supernatant containing SSEA-4 negative cells was transferred to a new tube and the process repeated 2-3 times to remove residual beads. Bead-bound SSEA4⁺ cells were released from magnetic field and both cells populations counted and processed for FACS and PCR analysis. The expression levels of SSEA4 in undifferentiated H1 cells, primitive gut cells and Stage IV cells, in both pre-sorted and sorted cell fractions is summarized in Table V.

In populations of cells isolated at stage II of the differentiation protocol outlined in Example 1, 20.5% of the cells expressed SSEA4 markers in prior to sorting. In contrast, only 1.8% of the cells expressed the SSEA4 post sort (Table V). The depletion resulted in removal of 91.2% of the SSEA-4 positive cells. In another experiment using endocrine precursor cells, 25.3% of cells expressed SSEA-4 prior to depletion, but only 0.9% expressed SSEA-4 after depletion, resulting in 95.5% removal of SSEA-4 positive cells (Table V). In contrast to differentiated cells, 91.2% of the population of undifferentiated embryonic stem cells expressed SSEA4.

The sorted SSEA4⁺ cells were highly enriched for the expression of pluripotency markers, including OCT4, NANOG, SOX2 and goosecoid (FIG. 12 panels a-d).

Example 5 Sorting of SSEA4^(+(HI)) and SSEA4^(−(LO)) Cells by FACS

In order to investigate and confirm the depletion of pluripotent-marker (SSEA-4+) enriched cells from differentiated cells by flow cytometry, cells were differentiated to Stage VI as described in Example 1. Cells were released from culture using TrypleE Express cell dissociation buffer and cells prepared for sorting as described in Example 2. The SSEA-4 antibody (R&D Systems, Minneapolis, Minn., Cat # FAB1435P) was used to isolate two cell fractions identified as SSEA-4(+)Hi and SSEA-4(−)Lo cells. Isolated cell fractions were analyzed for expression of pluripotency markers by RT-PCR as described in Example 4. Similar to SSEA-4 depleted and enriched fractions obtained using magnetic beads separation, as described in Example 5, the sorted SSEA-4(+)Hi cells were highly enriched for the expression of pluripotency markers OCT4, NANOG, SOX2 and goosecoid, unlike the SSEA-4(−)Lo cells. See FIG. 13 panels a-d.

Example 6 Transplantation of SSEA-4 Depleted Populations of Cells in Vivo

In pilot experiments, SSEA-4 depleted cells were differentiated to Stage IV of the differentiation protocol outlined in Example 1, and then transplanted into the kidney capsule of mice to test cell survival and engraftment. The data from the transplanted mice is summarized in Table VI.

Five to six-week-old male scid-beige mice (C.B-Igh-1b/Gbms Tac-Prkdc^(scid)-Lyst_(bg) N7) were purchased from Taconic Farms. Mice were housed in microisolator cages with free access to sterilized food and water. In preparation for surgery, mice were identified by ear tagging and their body weight measured and their blood glucose determine by a hand held glucometer (One Touch, LifeScan). Mice were anesthetized with a mixture of isoflurane and oxygen and the surgical site was shaved with small animal clippers. Mice were dosed with 0.1 mg/kg Buprenex subcutaneously pre-operatively. The surgical site was prepared with successive washes of 70% isopropyl alcohol, 10% povidone-iodide, and 70% isopropyl alcohol and a left lateral incision was made through the skin and muscle layers. The left kidney was externalized and kept moist with 0.9% sodium chloride. A 24G×¾″ I.V. catheter was used to penetrate the kidney capsule and the needle was removed. The catheter was then advanced under the kidney capsule to the distal pole of the kidney.

During the preoperative preparation of the mice, the cells were centrifuged in a 1.5 mL microfuge tube and most of the supernatant removed, leaving just enough to collect the pellet of cells. The cells were collected into a Rainin Pos-D positive displacement pipette and the pipette was inverted to allow for the cells to settle by gravity. The excess media was dispensed leaving a packed cell preparation for transplant.

For transplantation, the Pos-D pipette tip was placed firmly in the hub of the catheter and the cells dispensed from the pipette through the catheter under the kidney capsule and delivered to the distal pole of the kidney. The lumen of the catheter was flushed with a small volume of culture media to deliver the remaining cells and the catheter withdrawn. The kidney capsule was sealed with a low temperature cautery and the kidney was returned its original anatomical position. The muscle was closed with continuous sutures using 5-0 vicryl and the skin closed with wound clips. Mice were dosed with 1.0 mg/kg Metacam subcutaneously post-operatively. The mouse was removed from the anesthesia and allowed to fully recover.

Following transplantation, mice were weighed once per week and blood glucose measured twice a week. At various intervals following transplantation, mice were dosed with 3 g/kg glucose IP and blood drawn via the retro-orbital sinus 60 minutes following glucose injection into microfuge tubes containing a small amount of heparin. The blood was centrifuged and the plasma placed into a second microfuge tube and frozen on dry ice and then stored at −80° C. until human c-peptide assay was performed. Human c-peptide levels were determined using the Mercodia/ALPCO Diagnotics Ultrasensitive C-peptide ELISA according to the manufacturer's instructions.

At the time of sacrifice, blood was collected as described above and mice euthanized. The grafts were harvested from the kidney capsule and analyzed by real-time qPCR, immunohistochemistry, and pathology.

Three groups of mice were transplanted with about 3.3 million cells each comprising of i) cell clusters ii) single cells (undepleted) and iii) SSEA4 depleted single cells. Cells differentiated to Stage IV were either released with gentle scarping to make small cell clusters, or released with TrypleE into single cells for SSEA-4 depletion. Following SSEA-4 depletion as outlined in Example 5, both cell clusters and single cell prepations were replated in low attachment plates (Costar, Corning Incorporated, NY Cat #3471) overnight in precursor (Stage IV) cell differentiation medium prior to transplantation. The rock inhibitor Y-27632 dihydrochrolide monohydrate (Sigma, Cat # Y0503) was added to the culture overnight at a concentration of 10 μM. Following transplants, mice were monitored as described above for up to 12 weeks post transplants. Graft survival was not visibly demonstrated in the single cells recipients (depleted or undepleted) but was shown in 2 out of 5 mice receiving cell clusters. One out of 5 mice receiving cell clusters had detectable c-peptide levels at 12 weeks post transplantation. Poor graft survival was attributed to diminished cell quality and low numbers of cells transplanted in the pilot experiment.

The multi-step differentiation of human embryonic cells into mature, pancreatic endocrine cells through several intermediate steps including definitive endoderm (DE), pancreatic endoderm (PE) and pancreatic precursors is associated with dynamic changes in expression of surface markers. Although the differentiation protocol may produce as yet undefined, heterogeneous cell populations of multiple lineages including ectodermal and mesodermal cell types, tracking the changes in expression of surface markers in pancreatic differentiation medium could identify markers potentially useful in cell enrichment and purification. Table VII shows a summary of surface markers that either demonstrated an increase or decrease in expression, that may be useful for negative of positive selection of pancreatic endoderm cells. Markers that decreased in expression during the differentiation process include CD117, CD133, CD181, CD184, CD200, CD221, CD326, CD55, CD57, CD9, and CD98. Markers that increased in expression during the differentiation process include CD13, CD141, CD15, CD318, CD46, CD47, CD49c, CD49e, CD56, and CD73. These markers could singly or in various combinations be used to purify cell populations enriched for pancreatic endoderm and precursors.

Example 7 Flow Cytometric Sorting Procedures

Cells at different stages of maturation were gently released by incubation in TrypLE Express (Invitrogen #12604, CA) for 2-3 minutes at 37° C. and washed twice in BD FACS staining buffer containing 2% BSA (BD #554657, CA). Based on cell yields, 20-50×10⁶ single cells were re-suspended in 2-3 ml of blocking buffer (0.5% human gamma-globulin diluted 1:4 in staining buffer (BD, CA) for staining. Fluorophore conjugated primary antibodies were added to the cells at a final dilution of 1:20 and cells and incubated for 30 min at 4° C. Following washes, stained cells were re-suspended in 2-3 ml staining buffer and 50-60 μl of 7AAD added for live/dead cell discrimination prior to analysis and cell sorting. Isotype matched control IgG antibodies were used for negative control staining. For calculating fluorophore compensation values prior to sorting, cell were either left unstained or stained with single fluorophore of Fluoroscein isothiocyanate (FITC), Phycoerythrin (PE) or Allophycocyanin (APC) the nuclear dye 7-Aminoactinomucin D (7-AAD).

Cell sorting was done using the BD FACSAria cell sorter and the BD FACSDiva software. Isotype matched control cells were used to establish negative gates for each cell sorting. For each cell sorting experiment, the photomultiplier (PMT) voltage settings were adjusted using the appropriate fluorophore compensation values to produce a bright population (positive (+) or Hi) and dim population or cell subset (Negative (−) or Lo). Typically, positive cells populations (+ or Hi) were of the order of third decade or higher (10⁴) while negative population were in the first to second decade (10²-10³). Using established gates, cells were sorted using a 100 μM nozzle and a flow rate of 1.0. Following sorting, a small aliquot of cells were analyzed to assess the purity of the sorted cell subsets. RNA was collected from the presort and sorted cells using the Rneasy Mini Kit, Qiagen, CA) for RT-PCR analysis.

Publications cited throughout this document are hereby incorporated by reference in their entirety. Although the various aspects of the invention have been illustrated above by reference to examples and preferred embodiments, it will be appreciated that the scope of the invention is defined not by the foregoing description but by the following claims properly construed under principles of patent law.

TABLE I Flow Cytometric Characterization of Surface Marker Expression at Different Stages of Endodermal/Pancreatic Differentiation Mature Definitive Primitive Posterior Endocrine Endocrine Endocrine Endoderm Gut Tube Foregut Precursor) Cells Cells Antibody Synonyms Vendor/No. hES (Stage 1) (Stage2) (Stage 3) (Stage 4) (Stage 5) (Stage 6) BLT-R BD#552836 ND +/− +/− +/− +/− +/− +/− CD105 Endoglin Millipore#CBL418F +/− +/− +/− +/− +/− +/− +/− CD112 PRR2 BD#551057 +/− +/− +/− +/− +/− +/− +/− CD117 c-kit BD#341096 + ++ ++ + +/− +/− +/− CD118 LIFR, gp190 R&D#FAB249P +/− +/− + +/− +/− +/− +/− CD126 IL-6R BD#551850 +/− +/− +/− +/− +/− +/− +/− CD13 Aminopeptidase BD#555394 +/− +/− +/− +/− +/− +/− +/− N CD130 IL-6Rβ, gp130 BD#555757 +/− +/− +/− +/− +/− +/− +/− CD132 BD#555900 +/− +/− +/− +/− +/− +/− +/− CD133 AC133, MILTENYI#130- + + ++ + + + + prominin-like1 090-854 CD134 OX-40 BD#554848 +/− +/− +/− +/− +/− +/− +/− CD135 Flt3/Flk2 BD#558996 +/− +/− +/− +/− +/− +/− +/− CD137 BD#550890 +/− +/− +/− +/− +/− +/− +/− CD137 BD#559446 +/− +/− +/− +/− +/− +/− +/− Ligand CD140a PDGFRα BD#556002 +/− +/− +/− +/− +/− +/− +/− CD140b PDGFRβ BD#558821 +/− +/− +/− +/− +/− +/− +/− CD142 BD#550312 +/− +/− +/− +/− + + + CD146 MUC18 BD#550315 + + + +/− + + ND CD15 BD#551376 +/− + + + + + + CD161 BD#340536 +/− +/− +/− +/− +/− +/− +/− CD164 BD#551298 +/− +/− +/− +/− +/− +/− +/− CD178 FasL, CD95L BD#555293 +/− +/− +/− +/− +/− +/− ND CD180 BD#551953 +/− +/− +/− +/− +/− +/− +/− CD181 CXCR1, IL- BD#555939 +/− + +/− +/− +/− +/− ND 8RA CD183 CXCR3 BD#550967 +/− +/− +/− +/− +/− +/− +/− CD184 CXCR4, fusin BD#555976 +/− ++ + +/− +/− +/− + CD185 CXCR5 BD#551959 +/− +/− +/− +/− +/− + ND CD193 CCR3 BD#558165 +/− + +/− +/− +/− +/− +/− CD195 CCR5 BD#555992 +/− +/− +/− +/− +/− +/− ND CD1b BD#555969 +/− +/− +/− +/− +/− +/− +/− CD20 BD#555622 +/− +/− +/− +/− +/− +/− +/− CD200 OX-2 BD#552475 + ++ ++ + + ++ ++ CD205 BD#558069 +/− +/− +/− +/− +/− +/− +/− CD220 Insulin-R BS#559955 +/− +/− +/− +/− +/− +/− ND CD221 IGF-1 Rα BD#555999 + ++ ++ + +/− + +/− CD24 BD#555428 +++ +++ +++ +++ +++ +++ +++ CD243 MDR-1; P-gp BD#557002 +/− +/− +/− +/− +/− +/− +/− CD252 OX-40 Ligand BD#558164 +/− +/− +/− +/− +/− +/− +/− CD26 BD#555436 +/− +/− +/− +/− +/− +/− +/− CD271 NGFR BD#557198 +/− ND +/− +/− +/− +/− ND CD275 BD#552502 +/− +/− +/− +/− +/− +/− +/− CD28 BD#555728 +/− +/− +/− +/− +/− +/− +/− CD29 Integrin β1 BD#559883 +++ +++ +++ +++ +++ +++ +++ CD305 LAIR1 BD#550811 +/− +/− +/− +/− +/− +/− ND CD309 VEGFR2, BD#560494 +/− +/− +/− +/− +/− +/− +/− KDR CD318 CDCDP1 R&D#FAB26662P +/− +/− +/− +/− + + + CD326 Ep-CAM BD#347197 +++ +++ +++ ++ ++ ++ ++ CD33 BD#555450 +/− +/− +/− +/− +/− +/− +/− CD332 FGFR2, R&D#FAB684A +/− +/− +/− +/− +/− +/− +/− KGFR2 CD340 ErbB-2, BD#340553 +/− +/− +/− +/− +/− +/− +/− HER2/neu CD36 BD#550956 +/− +/− +/− +/− +/− +/− + CD39 BD#555464 +/− +/− +/− +/− +/− +/− ND CD42b BD#555472 +/− +/− +/− +/− +/− +/− +/− CD43 BD#555475 +/− +/− +/− +/− +/− +/− ND CD44 BD#559942 +/− +/− +/− +/− +/− +/− +/− CD46 BD#555949 + +/− +/− +/− + + ND CD47 BD#556046 +/− +/− + +++ ++ ++ ++ CD49b α2 Integrin, BD#555669 + +/− + + + + +/− VLA-2 CD49c α3 Integrin, Abcam#ab30489 + + + + + + + VLA-3 CD49e α5 Integrin, BD#555617 + +++ +++ ++ + + + VLA-5 CD49f α6 Integrin, BD#555735 + +/− + + + + +/− VLA-6 CD55 BD#555696 + ++ + +/− + + + CD56 NCAM BD#555518 + + + + +++ ++ +++ CD57 BD#555619 +++ +++ +++ ++ + + + CD58 LFA-3 BD#555920 + +/− +/− +/− +/− +/− +/− CD63 LIMP. LAMP-3 BD#557288 ND +/− +/− +/− +/− +/− +/− CD66 BD#551480 +/− +/− +/− +/− +/− +/− +/− CD71 BD#551374 + + + + +/− + + CD73 BD#550257 +/− +/− +/− + + + ND CD74 BD#555540 +/− +/− +/− +/− +/− +/− ND CD88 C5aR BD#550494 +/− + +/− +/− +/− +/− +/− CD9 P24, MRP-1 BD#555372 + + +/− +/− +/− +/− +/− CD91 BD#550496 +/− +/− +/− +/− +/− +/− +/− CD95 Apo-1, Fas BD#555674 +/− +/− +/− +/− +/− +/− ND CD98 BD#556076 +++ +++ +++ +++ ++ ++ + CD99 MIC2, E2 +/− +++ +++ +++ +++ +++ ++ CDw210 IL-10 R BD#556013 +/− + +/− +/− +/− +/− +/− DLL1 R&D#FAB1818A ND ND ND +/− +/− +/− ND EGFR ErbB-1, BD#555997 +/− +/− +/− +/− +/− +/− +/− HER1 fMLP BD#556016 +/− +/− +/− +/− +/− +/− +/− MICA/B BD#558352 +/− + +/− +/− +/− +/− ND Notch1 BD#552768 +/− + +/− +/− +/− +/− ND SSEA-4 R&D#FAB1435P +++ +++ ++ + + + + TGFBR3 Lifespan#LS- +/− ND + +/− +/− + ND C76502 TRA1-60 BD#560193 +++ +++ + + + + + TRA1-81 BD#560161 +++ +++ + + + + + TWEAK BD#552890 +/− +/− +/− +/− +/− +/− +/− Key: ND = Not Determined; +/− = 0-10%; + = 10-50%; ++ = 50-85%; +++ = 85-100%

TABLE II Surface Markers used to Enrich for Pancreatic Cell Precursors Surface Markers Phenotype of Used (Single/ Vendor/ Enriched % Starting % Sorted Fold Combinations) Stage of Cells Sorted No. Populations Population Population Enrichment CD56/CD13 Endocrine Precursors (S4) BD#555518/ CD56⁺CD13⁻ 64.1 82.1 ~1.3 #55593 CD133 Endocrine Precursors (S4) Miltenyi#130- CD133⁻ 48.6 92.0 ~1.9 090-854 CD49c(α-3 Integrin) Endocrine Precursors (S4) Abcam#ab30489 CD49c^(Lo(−)) 31.7 95.9 ~3.1 CD56/CD15 Endocrine Precursors (S4) BD#555518/ CD56⁺CD15^(Lo(−)) 26-80 ND ND #551376 CD15 Endocrine Precursors (S4) BD#551376 CD15⁻ 89.6 97.5 ~1.1 CD56/CD57 Endocrine Precursors (S4) BD#555518/ CD56⁺CD57⁺ 31.3 59.1 ~1.9 Endocrine Cells (S5) #555619 CD98 Endocrine Cells (S6) BD#556076 CD98⁺ 61.3 98.9 ~1.6 CD47 Endocrine Cells (S5, S6) BD#556046 CD47⁻ 22.8 75.1 ~3.3

TABLE III Expression levels of LIF Receptor Stage of Differentiation Stage 2, Stage 2, Stage 3, Stage 4, Day 2 Day 3 Day 4 Day 3 Expression 47% 70% 5% 1% Level (%)

TABLE IV Expression Levels of CD184 Before and After Enrichment Enriched CD184+ CD184− Pre-sort Fraction Fraction Description CD184+CD56− CD184+CD56+ CD184−CD56− CD184−CD56+ CD184+ CD184+ Expression (%) 1% 8% 20% 70% 79% 0.6%

TABLE V Expression Levels of SSEA-4 Antigen Stage of SSEA-4 Expression (%) % Fold Cells Differentiation Pre-Depletion Post-Depletion Depletion H1 Undifferentiated 91.2 ND ND H1 Primitive Gut 20.5 1.8 91.2 (Stage II) H1 Endocrine 20.1 0.9 95.5 Precursors (Stage IV)

TABLE VI Summary Data of Mice Transplanted with SSEA-4 Depleted Cells Total Cell No. of Grafts at C-Peptide Group Cell Type No. Mice 12 Week at 12 Weeks 1 Cell 3.3 million 5 3/5 mice 1/5 mice Clusters visible detectable c- grafts peptide 2 Single 3.3 million 5 0/5 mice 0/5 mice Cells with visible detectable c- Un- grafts peptide depleted 3 SSEA-4 3.3 million 2 0/2 mice 0/2 mice Depleted with visible detectable c- Single grafts peptide Cells

TABLE VII Surface Markers Associated with Differentiation of Human Embryonic Stem cells into Pancreatic and Endodermal Lineages. Surface Markers Changes Surface Markers Changes During Associated Used To Enrich Cell Differentiation with Surface Pancreatic Fractions DE→PE→Endocrine Markers* Endoderm/Endocrine Enriched CD117 Decrease ND — CD13 Increase Yes CD13− CD133 Decrease Yes CD133− CD142 Increase ND — CD15 Increase Yes CD15− CD181 Decrease ND — CD184 Decrease Yes CD184+ CD200 Decrease ND — CD221 Decrease ND — CD318 Increase ND — CD326 Decrease ND — CD46 Increase ND — CD47 Increase Yes CD47− CD49c Increase Yes CD49c− CD49e Increase ND — CD55 Decrease ND — CD56 Increase Yes CD56+ CD57 Decrease Yes CD57+ CD73 Increase ND — CD9 Decrease ND — CD98 Decrease Yes CD98+ Changes associated with Surface Markers Denotes if Expression level of the particular Surface Marker Increased or Decreased as cell were differentiated from Definitive Endoderm (DE, Stage I) to Pancreatic Endoderm (PE, Stage III) and finally to Endocrine Cells (Stage V/VI). 

What is claimed is:
 1. A method of enriching a population of primitive gut tube cells comprising: a) differentiating a population of human pluripotent stem cells into definitive endoderm cells with a TGF-β receptor agonist; b) differentiating the definitive endoderm cells into a population containing primitive gut tube cells; c) enriching the population of primitive gut tube cells by contacting the population of cells with a reagent that is capable of binding the Lif receptor, and selecting for primitive gut tube cells that are bound to the reagent capable of binding the Lif receptor.
 2. The method of claim 1, wherein the method further comprises culturing the population of human pluripotent stem cells prior to differentiation.
 3. The method of claim 1, wherein the TGF-β receptor agonist is activin A.
 4. The method of claim 1, wherein the cells are enriched using flow cytometry or FACS.
 5. The method of claim 1, wherein the human pluripotent stem cells are human embryonic stem cells.
 6. The method of claim 1, wherein the method further comprises differentiating the enriched population of primitive gut tube cells into pancreatic endoderm cells, pancreatic endocrine precursor cells or pancreatic endocrine cells.
 7. The method of claim 6, wherein the method comprises differentiating the enriched population of primitive gut tube cells into pancreatic endocrine precursor cells.
 8. A method of enriching a population of human primitive gut tube cells comprising differentiating a population of human pluripotent stem cells into a population containing human primitive gut tube cells, contacting the population of cells with a reagent that is capable of binding the Lif receptor, and selecting for primitive gut tube cells that are bound to the reagent capable of binding the Lif receptor.
 9. The method of claim 8, wherein the cells are enriched using flow cytometry or FACS.
 10. The method of claim 8, wherein the primitive gut tube cells are obtained by step-wise differentiation of human pluripotent stem cells.
 11. The method of claim 10, wherein the human pluripotent stem cells are human embryonic stem cells.
 12. The method of claim 8, wherein the primitive gut tube cells are obtained by a method comprising a) differentiating the population of human pluripotent stem cells into definitive endoderm cells by treating the human pluripotent stem cells with a medium supplemented with activin A; and b) differentiating the population of definitive endoderm cells into a population containing primitive gut tube cells.
 13. The method of claim 12, wherein the method further comprises culturing the population of pluripotent stem cells.
 14. The method of claim 8, wherein the method further comprises differentiating the enriched population of human primitive gut tube cells into human pancreatic endoderm cells, human pancreatic endocrine precursor cells, or human pancreatic endocrine cells.
 15. The method of claim 14, wherein the method further comprises differentiating the enriched population of human primitive gut tube cells into human pancreatic endocrine precursor cells. 